1. Field of the Invention
The present invention relates to the technological field of an overlay network system. A peer to peer communication system is one example of an overlay network system. The peer-to-peer communication system includes a plurality of node devices that can communicate with each other through a network.
2. Description of the Related Art
Recently, attention has been drawn to the peer-to-peer communication system. Specifically, by conventional technologies, a plurality of node devices are subdivided into groups based on a distance between the node devices on the network. Accordingly, when a pre-determined one of the node devices sends or relays information, it will transmit the information to the node device representative of each of the groups.
In a peer-to-peer communication system, an overlay network is built on a physical network. The overlay network is a logical network. The physical network may in some cases be configured by interconnecting a plurality of networks. The plurality of networks may be, for example, local area networks (LANs) or access networks. However, such circumstances would not be taken into account in grouping by the conventional technologies. Therefore, there are some cases, for example, where the node devices may communicate with each other through different networks although they can communicate with each other in the same network. In such a case, there is a high possibility that information transmitted from the node device may pass through a communication line that interconnects the networks. In this case, when the communication line has a small bandwidth, sometimes the information may not be transmitted or received sufficiently between the networks.